1. Field of the Invention
The present invention relates to an improvement in a computer-aided image diagnosis system that detects an abnormal shadow candidate in a radiation image, based on image information representing the radiation image.
2. Description of the Related Art
In the medical field, a wide variety of image-forming modalities (image input units), such as computed tomography (CT), computed radiography (CR) and the like, have spread as units that generate an image for diagnosis.
In addition, computer-aided image diagnosis systems have been proposed in which, based on image information representing a diagnostic radiation image acquired by the image-forming modality, an abnormal shadow candidate appearing in the radiation image is automatically detected by a computer, and the image, etc., of the detected abnormal shadow candidate are displayed on a display unit or recorded on a storage medium such as film (Japanese Unexamined Patent Publication Nos. 8(1996)-294479 and 8(1996)-287230).
The words xe2x80x9cabnormal shadowxe2x80x9d mean a shadow appearing in a radiation image because of an abnormal part or the like on which a cancer has grown or is growing. For example, in a mammogram (which is a radiation image of the breast obtained by mammography), the intumescence shadow or micro-calcification shadow corresponds to the abnormal shadow.
For instance, for a mammogram, the computer-aided image diagnosis system represents a density gradient (or a brightness gradient) in an image as a density gradient vector, and detects an image portion where the degree of concentration of the density gradient vector is high, as the intumescence shadow candidate, using an iris filer. Also, with a morphologic algorithm employing multiplex elements in accordance with the size of a micro-calcification shadow to be detected, an image portion whose density varies in a range spatially narrower than the multiplex elements is detected as the micro-calcification shadow.
In the case where the abnormal shadow candidate is detected in this manner, it is output (e.g., displayed) as a diagnostic image in various forms, along with or separately from the entire radiation image (Japanese Unexamined Patent Publication No. 8(1996)-294479, etc.).
The computer-aided image diagnosis system, incidentally, must handle an image of very high quality for the process of detecting the aforementioned abnormal shadow candidate and to observe the detected abnormal shadow candidate in detail. That is, since the image information representing a radiation image has a large number of pixels and high gradation (number of bits) , the data size is much larger. Also, a display unit to display a diagnostic image has to have high resolution to express a high-quality image, and furthermore, a large-capacity storage medium is employed to store image information.
In the conventional computer-aided image diagnosis system, in order to observe and read uniformly in detail a large-data-size diagnostic image whether an abnormal shadow candidate is detected or not, the diagnostic image is output in various display forms to a high-quality display unit having high resolution and high gradation and is stored in a storage medium.
However, since the diagnostic image is large in data size, as described above, displaying the diagnostic image on the aforementioned display unit much higher in display quality results in slow output response and becomes a problem particularly in the case where a great number of diagnostic images are handled within a limited time, like a group examination. In addition, if all diagnostic images are stored uniformly in large data size in a storage medium, the time required for the storing operation will become longer and there will be a problem that the amount of storage medium used up increases.
The present invention has been made in view of the aforementioned problems. Accordingly, it is an object of the present invention to provide a computer-aided image diagnosis system that is capable of performing proper output for each diagnostic image to be observed and read. Another object of the invention is to provide a computer-aided image diagnosis system which is capable of performing proper storage for each diagnostic image to be observed and read.
To achieve the aforementioned objects and in accordance with one important aspect of the present invention, there is provided a first computer-aided image diagnosis system which switches a destination where a diagnostic image is output, in accordance with the result of detection of an abnormal shadow candidate.
The first computer-aided image diagnosis system comprises: means for detecting an abnormal shadow candidate in a radiation image, based on image information representing the radiation image; means for switching a destination where a diagnostic image is output, in accordance with a result of the detection of the abnormal shadow candidate; and means for outputting the diagnostic image which corresponds to the detection result.
The process of detecting an abnormal shadow candidate in a radiation image, based on image information representing the radiation image, can employ, for example, the process of detecting an intumescence shadow candidate by employing an iris filer or the process of detecting a micro-calcification shadow candidate by a morphologic algorithm, disclosed in the aforementioned Japanese Unexamined Patent Publication Nos. 8(1996)-294479 and 8(1996)-287230.
The words xe2x80x9cdiagnostic image which corresponds to the result of detection of an abnormal shadow candidatexe2x80x9d mean various images, such as an original radiation image, an image obtained by performing a marking process or an emphasizing process, etc., on an abnormal shadow candidate detected from an original radiation image, an image obtained by extracting a detected abnormal shadow candidate alone, an image disposed so that an original image and an abnormal shadow candidate extracted from the original image can be output to a single display screen or storage medium, and so on.
The aforementioned xe2x80x9cdestination where a diagnostic image is outputxe2x80x9d refers to a plurality of display units differing from one another in display quality, or these display units provided with a storage unit which stores the aforementioned diagnostic image on a predetermined storage medium. Therefore, in accordance with the result of detection of an abnormal shadow candidate, the switching means is capable of switching one of the plurality of display units which displays the diagnostic image. The switching means is also capable of switching one of the plurality of display units which displays the diagnostic image and switching whether or not the diagnostic image is stored on a predetermined storage medium.
The words xe2x80x9cdisplay qualityxe2x80x9d refer to image quality, such as resolution, gradation and the like, speed required for displaying, etc.
The expression xe2x80x9cswitch in accordance with the result of detection of an abnormal shadow candidatexe2x80x9d means switching according to whether or not an abnormal shadow candidate has been detected, i.e., whether the number of abnormal shadow candidates is 1 or more, or 0. Also, switching may be performed according to the number of abnormal shadow candidates detected. Furthermore, the switching may be three or more switchings as well as two switchings.
In accordance with another important aspect of the present invention, there is provided a second computer-aided image diagnosis system which switches the data storage size of a diagnostic image in accordance with the result of detection of an abnormal shadow candidate.
The second computer-aided image diagnosis system comprises: means for detecting an abnormal shadow candidate in a radiation image, based on image information representing the radiation image; means for switching the data size of the diagnostic image to be stored as the diagnostic image, in accordance with a result of the detection of the abnormal shadow candidate; and means for storing the diagnostic image which corresponds to the detection result.
The words xe2x80x9cswitch data sizexe2x80x9d mean that data size is switched, for example, by varying the compression size of data. In addition, data size after compression may be switched indirectly by switching a method of compression, such as reversible compression, irreversible compression and the like.
According to the first computer-aided image diagnosis system of the present invention, a destination where a diagnostic image is output can be switched according to the result of detection of an abnormal shadow candidate. Therefore, proper output can be performed for each diagnostic image that is to be observed and read. More specifically, for example, a diagnostic image for a radiation image, from which an abnormal shadow candidate was detected, is output to a high-quality display unit to observe and read the existence of the abnormal shadow candidate in detail, as before. On the other hand, a diagnostic image for a radiation image, from which no abnormal shadow candidate was detected, is output to a display unit relatively inferior in display quality to the aforementioned high-quality display unit to recognize and read the nonexistence of an abnormal shadow candidate in a simple manner. In this way, the demand for a diagnostic image that is to be observed and read in detail is compatible with the demand for a quick output response.
According to the second computer-aided image diagnosis system of the present invention, the data size of a diagnostic image to be stored can be switched in accordance with the result of detection of the abnormal shadow candidate. Each diagnostic image, which is to be observed and read, can be stored in an appropriate data size. More specifically, for instance, a diagnostic image for a radiation image, from which an abnormal shadow candidate was detected, is stored in data size as before, or in a reversibly compressed data size, and afterwards, the stored data can be read out to observe and read the existence of the abnormal shadow candidate in detail. On the other hand, a diagnostic image for a radiation image, from which no abnormal shadow candidate was detected, is stored in data size smaller than before, or in irreversibly compressed data size. In this way, the demand for higher reproducibility of diagnostic image data, which is to be observed and read, is compatible with the demand for a quick input-output response of storage and less consumption of a storage medium.